THE STAR-FORMING DWARF GALAXY POPULATION IN THE LOCAL UNIVERSE AND BEYOND: The first 3D Spectroscopic study of a sample of nearby Star-Forming Dwarfs Luz Marina Cair ó s Barreto ASTROPHYSIKALISCHES INSTITUT POTSDAM

STAR-FORMING DWARF GALAXIES Starbursts Low luminosity (M B > -18) Optical H II regions spectra Gas-rich objects Metal-deficient (Z  /50 < Z < Z  /3) Star-forming rates: M  /yr Blue Compact Dwarfs / H II galaxies / Amorphous galaxies

OPEN QUESTIONS 1.What is their evolutionary status? Are all of them old or do young galaxies exist? 2.What are their star-forming histories? 3.What is their dust content and distribution? 4.Are there evolutionary connections between SFDs and other types of dwarfs? 5.What mechanisms trigger the starburst? Are interactions and mergers playing a role ? INTEGRAL FIELD SPECTROSCOPY

SCIENTIFIC BACKGROUND 90s- … Surface brightness photometric studies in the optical and in the NIR of large samples Papaderos et al. 1996ab; Doublier et al 1997,99; Telles 1997; Marlowe et al. 1997, 1999; Ostlin 1998; Noeske et al. 2003, 2005; Bergvall & Ostlin 2002; Cairós et al 2000, 2001ab, 2003, 2005; Gil de Paz et al. 2003, 2005; Caon et al. 2005; Amorin et al Structural properties of the host: exponential or Sersic ? ; 1D vs 2D modelling SPECTROPHOTOMETRIC ANALYSES ARE ESSENTIAL Characterize the young stars ( Characterize the young stars (H , WR features … ) Gaseous emission (Cairós et al. 2002, 07) Gaseous emission (Cairós et al. 2002, 07) Dust (Hunt et al. 2001, Cairós et al. 2003, Johnson et al. 2004, Vanzi & Sauvage 2004) Dust (Hunt et al. 2001, Cairós et al. 2003, Johnson et al. 2004, Vanzi & Sauvage 2004) Absorption features tracing the old stars Absorption features tracing the old stars Méndez et al. 1999: IIZw33; Gil de Paz et al. 2000: Mrk86; Papaderos et al. 1988: SBS ; Cairós et al. 2002: Mrk370; Cairós et al. 2007: Mrk35

Broad-band imaging: UBVRI + NIR Narrow-band frames long slit spectroscopy + evolutionary synthesis models Prohibitive exposure times: 2-3 nights per object = individual objects Long-slit spectroscopy: Sequentiality + Accuracy of the slit position Non-homogeneity of the whole data collection DRAWBACKS SPECTROPHOTOMETRIC ANALAYSIS OF STATISTICALLY MEANINGFUL SAMPLES ARE NOT FEASIBLE SPECTROPHOTOMETRIC ANALYSIS OF SFDs

INTEGRAL FIELD SPECTROSCOPY Homogeneity Shorter exposure times Allington-Smith et al Record simultaneously three variables ( ,  and ) in two dimensions (x and y)

THE POWER OF IFU SPECTROSCOPY One exposure = imaging and spectra over a wide wavelength range. Now, for the first time, spectro-photometric studies of large samples of SFDs are feasible IFU observations are one order of magnitude more efficient than traditional techniques

THE FIRST 3D SPECTROPHOTOMETRIC MAPPING OF A LARGE SAMPLE OF STAR FORMING DWARFs THE SAMPLE: 60 Galaxies Luminosity range: MB = to –20.50 Metallicity: 0.05 – 0.85 Z  All morphological subclasses (Cairós et al. 2001b) Additional deep imaging in at least two bands

IMMEDIATE AIMS Build flux and equivalent width maps of emission lines: H , H , H , [OIII] or the shock-heated [SII], [OII] Age, SFR, trigger of SF Build maps of the most interesting line ratios: [OIII]/ H  or [NII]/ H  Ionization mechanism Build continuum maps (lines free passband or interpolating across emission lines) Morphology and stellar content Mrk314

IMMEDIATE AIMS Map the reddening Dust content and distribution Map the physical parameters of the gas (Te,Ne) Map WR features, Å Ages and IMF parameters Chemical abundances Search for absorption features tracing the cooler stars: Mg 5167, 5184 Å, Fe 5270, 5335 Å, Na 5890, 5896 Å, CaT Ages and metallicity of the old stars

IMMEDIATE AIMS Gas velocity fields + Stars velocity fields Mechamism that trigger the SF, interactions? Starburst99 GALEV

OBSERVATIONS - INSTRUMENTATION OBSERVATIONS - INSTRUMENTATION INTEGRAL, 4.2m WHT, ORM FOV rectangular STD/SB2 0.9´´ FOV: 16.0 x 12.3 Number of fibers: 219 ( ) STD/SB3 2.7´´ FOV: 33.6 x 29.4 Number of fibers: 135 ( ) Spectral range: 4300 – –6900 Linear dispersion: 3 A/pix Typical exposure times: 2 hours Mrk297, IIIZw102, Mrk314, Mrk370, Mrk35 Mrk33, Mrk140, UM462, Mrk131, Mrk36, Mrk35

OBSERVATIONS - INSTRUMENTATION OBSERVATIONS - INSTRUMENTATION PMAS 3.5m CAHA PMAS/Lens array FOV rectangular 1.0´´/lens FOV: 16.0 x 16.0 Number of fibers: nights allocated in March objects Spectral range: 3600 – 7000 Linear dispersion: 3A/pix Typical exposure times: 2 hours PPAK IFU FOV hexagonal 2.7´´ FOV: 74.0 x 65.0 Number of fibers: Mrk32, Mrk177, Mrk475, Izw123, Mrk209, Mrk450, Mrk747 Mrk5, Haro33, Mrk170 IIZw71, Mrk149, Mrk157, Mrk186

OBSERVATIONS - INSTRUMENTATION OBSERVATIONS - INSTRUMENTATION VIRUS-P, 2.7 Harlan J. Smith, McDonald Observatory, Texas FOV hexagonal 4.10´´ FOV: 112 x 112 Spectral range ~ Linear dispersion: 1.2 A/pix Number of fibers: 247 Typical exposure times: 3-4 hours On-going program during the instrument commissioning: Larger objects as IIZw33, IIIZw102, Mrk153, Mrk401 …

OBSERVATIONS - INSTRUMENTATION OBSERVATIONS - INSTRUMENTATION VIMOS, 8.2m VLT, ESO FOV rectangular 0.67´´ FOV: 27.0 x 27.0 Spectral range ~ 4200 – 7400 Linear dispersion: 3A/pix Number of fibers: 6400 Typical exposure times: hours Allocated 3 nights, August: high signal to noise observations Tololo , Mrk900, Mrk1131, Haro14, Haro15, Tololo

ANALYSIS AND FIRST RESULTS ANALYSIS AND FIRST RESULTS 1. We study the properties of selected regions: flux, eqw, line ratios … Densities, ionization mechanism, abundances

FIRST RESULTS FIRST RESULTS 1. M aps of ionized gas Mrk 297: [OIII] + H 

FIRST RESULTS FIRST RESULTS 2. Continuum maps IIIZw102: ``pure continuum´´´maps V-band map

FIRST RESULTS FIRST RESULTS 3. Line ratio maps Mrk297Mrk35

FIRST RESULTS FIRST RESULTS 4. Extinction maps Mrk297Mrk314IIIZw102

FIRST RESULTS FIRST RESULTS 5. Ionized gas kinematics III Zw 102Mrk 297

FIRST RESULTS FIRST RESULTS 5. Ionized gas kinematics Mrk 314Mrk 35

Summary: the pilot study of five SFDs Summary: the pilot study of five SFDs The spectra: The strength of emission lines and absorption features, as well as the continuum shape or the presence of relevant lines significantly vary across each galaxy: The studied regions present HII-like ionization Ne variations: cm -3 Oxygen abundances do not change from knot to knot 3D maps: Continuum and emission lines morphologies are different. Line ratio maps have structure All the galaxies present a complex extinction pattern and high values of C(H  ). High metallicities: 0.17 to 0.87 Zsolar Four galaxies have distorted velocity fields. These galaxies display properties typical of the so-called LBCDs, very different from “normal” BCDs/Hii galaxies.

And a final remark … The relevance of SFDs in a general astrophysical framework Star-formation process Chemical enrichment of the Inter Galactic Medium Cosmology Galaxy formation and evolution: dwarfs are the building blocks out of which larger galaxies are assembled Big Bang Nucleosynthesis but also, the more massive, more metallic SFDS ~ counterpart of the LBCs Essential template to interpret the results of studies at higher redshifts

The Team The Team Astrophysikalisches Institut Potsdam : M. Roth, A. Kelz, P. Weilbacher, A. Monreal-Ibero, H. Zinnecker Instituto de Astrofísica de Canarias: N. Caon, B. García-Lorenzo, C. Muñoz-Tuñón Instituto de Astrofísica de Andalucía: J.M. Vílchez, C. Kherig, P. Papaderos Alexander von Humboldt Foundation